As a result of increased environmental awareness and the trend toward conserving natural water resources, the rainwater running off a roof is usually no longer conducted to a water treatment plant via the sewerage system, but rather increasingly is collected. It is then often used for watering gardens or filling ponds or used in the household as utility water, for example, for flushing toilets.
Usually rainwater is collected as roof runoff water. It contains, in addition to heavy metal dust from the atmosphere, dust accumulated on the roof surfaces coming from the environment or from the roofing materials.
It is known that metallic materials, such as zinc, lead, or copper, which are used as roofing materials or in the construction of gutters, are subject to corrosion due to the effect of air and rain. The amount of metal ions released into the roof runoff water as a result depends on different factors, which include the intensity and amount of the respective precipitation. For this very reason, the environmental friendliness of metallic roofing materials is presently the subject of much critical discussion.
In those cases where roof runoff water is not collected, it is conducted directly to water treatment plants via the sewerage system. Roof runoff water is, however, increasingly drained away directly, so that release of heavy metals into the environment cannot be avoided. Minimizing the release of heavy metals into the soil or natural waters would therefore reduce environmental pollution and reduce the metal content in the sludges produced in water treatment plants. Minimized heavy metal release allow roof runoff water to be used for different applications. Thus, for example, the usage of drinking water, treated at a high cost, for different purposes in the house and garden could be substantially reduced.
It is known that neutralizing systems can be installed at water treatment plants to precipitate heavy metals. This can, however, only be done centrally due to the size of such systems. These are expensive systems to build. In addition, they cannot capture roof runoff water.
Progressing from the related art, the object of the present invention is to provide an arrangement for removing heavy metal ions from roof runoff waters that can be easily and relatively inexpensively installed directly on the building either in new or existing structures.
The present invention provides an apparatus for removing heavy metal ions from roof runoff waters. A filter having a filter material made of synthetic or natural crystalline hydrated aluminum silicates and having a skeleton structure containing alkaline or alkaline earth ions is used according to the present invention. Such a filter is arranged immediately downstream from a gutter system. The advantage of such a filter material is that it is easy to handle, inexpensive, regeneratable, and hygienically non-objectionable. The roof runoff water thus purified can be used for different purposes in the household, garden, or pond without causing considerable environmental pollution. The invention also makes it possible to easily drain off roof runoff water into the soil or into natural waters.
The filter material can be regenerated and reused in filters via repeated ion exchange. Thus ion exchange costs are kept low and natural resources are saved. Furthermore, chemically bound heavy metals can be recovered so that they can be reused with only negligible amounts of waste being generated.
The filter material is preferably formed by compounds of the zeolite group. However, other materials with ion exchange properties can also be used. Natural zeolite include, for example, chabasite, mordenite, heulandite, clinoptilolite, laumontite, natrolite, analcim, philipsite, and/or also clays such as bentonite. One zeolith alone or different zeoliths can be used as mixtures. Depending on the size of the surface exposed to precipitation, the type of roof metal (zinc, copper, or lead) and the metal content of the roofing material or gutter, the amounts of filter material naturally vary.
According to a further aspect of the invention, it can be of advantage if absorbing means are added to the filter material. These may include, for example, activated carbon, iron oxide, or dolomite. Clinoptilolith or mixtures of clinoptilolith and other zeoliths are preferably used.
According to a further aspect of the invention, an arrangement is provided that is particularly well suited for surfaces exposed to precipitation measuring less than about 160 sq.m. This size corresponds to the DN 100 downpipe normally used in these cases. The filter is designed as a double-pipe cartridge with an inner pipe and an outer pipe with a filter material filled in the annular space between the inner pipe and the outer pipe. It is attached to the cast iron gutter pipe located above the ground surface of a gutter system so that it can be replaced. The cast iron gutter pipe normally terminates a DN 100 downpipe at the ground surface. Since the cast iron gutter pipe is usually coupled to the downpipe via a sliding cast iron gutter pipe cap, the cast iron gutter pipe can be turned after sliding the cast iron gutter pipe cap upward and the filter can then be easily changed.
In the event of a normal rainfall, the roof runoff water flows along the inside of the downpipe and reaches the annular space filled with filter material between the inner pipe and the outer pipe. The flow rate can be selected so the amount of normal rainfall is collected without problems. In the event of heavy rainfall, the excess water can be easily drained off via the inner pipe. Internal research has shown that such roof runoff water only contains low metal concentrations in such cases, which can be drained off unfiltered without objections. The inner pipe also allows leaves and sticks to be easily removed through the inner pipe to the sewerage system in the event of heavy rainfall.
One advantageous property of the filter material is that it can run dry after a rain event. Drying out of the filter has no effect on the separating performance or metal absorption by the filter material. Rather, drying out of the filter has a certain advantage concerning potential clogging of the filter by dirt particles in the roof runoff water. The fact that such dirt particles are being continuously dried out and thus their consistency is being changed, reduces the risk of clogging.
The dimensions of the filter and thus its capacity depend on the outer diameter of the cast iron gutter pipe and on the inner diameter of the inner pipe. In order to reliably prevent clogging by leaves and sticks, the inner diameter of the inner pipe must be at least 30 mm. A maximum inner diameter of 100 mm is adequate. Due to the usual distance of the downpipe to the adjacent building wall and from the esthetic point of view, the outer diameter of the cast iron gutter pipe can be between approximately 100 mm and 250 mm. The height of the filter is between approximately 300 mm and 1800 mm. Within these extremes, the size of the filter is adapted to the conditions of the application, in particular to the surface exposed to rainfall.
The filter is preferably designed such that the lower end of the outer pipe is crimped inward. Thus it forms a stop for the inner pipe that is crimped outward at the lower end. The radial dimension of the annular space between the inner pipe and the outer pipe is also determined by a spacer, which is provided at the upper end of the inner pipe. This spacer can be formed by an annular disk, for example, which is attached to the external perimeter of the inner pipe. Such a filter is easy to manufacture and replace.
Another arrangement is provided that is preferably used if the surface exposed to precipitation is greater than approximately 160 sq.m. and if the roofing material is mainly made of metal. The collector well is usually at the end of the gutter system below ground surface and has a removable cover. A filter is usually installed in such a collector well so that a compact filter material column is present. This column is arranged at a distance from the inside of the collector well at least in some areas so that this distance is used for overflow. Due to the compact column, this filter is capable of filtering large amounts of roof runoff water. Distance specifications or esthetic considerations do not need to be taken into account, since the collector well has sufficient volume to accommodate the necessary amount of filter material. By modifying the filter cross section surface, it can be adapted to the local metal load and the surface area exposed to precipitation over a broad range.
The cover of the collector well allows the filter material to be regularly monitored and replaced as needed.
The height of the compact column in the collector well can be between 200 mm and 1000 mm. The diameter of the column is between 100 mm and 600 mm.
In order for the roof runoff water supplied to the filter to be distributed over the entire cross section of the compact filter column as evenly as possible, a water distributor is arranged above the filter. This can be a distributor spiral, for example. This prevents roof runoff water from dripping only on a certain area of the filter, which is then rapidly saturated and the filtering performance of the filter drops, although its total capacity is far from being exhausted.
Due to the compact design of the filter, there is the danger that dirt and leaves will accumulate on the surface of the filter material and thus clog it. To avoid this problem, a foreign body passage is provided in the lower portion of the gutter system. This foreign body passage can be arranged either directly in the downpipe of the gutter system or directly at the inlet of the collector well.
In cases where a rainwater use system is available or at least planned, it is advantageous if the filter is arranged in a container and located downstream from a water storage device located at the lower end of the gutter system with a pump connected between them. Such a water storage device has a capacity of approximately 1500 liters. The roof runoff water goes from the gutter system into the water storage device and is pumped therefrom by the pump into a container equipped with filter material, wherefrom it can be supplied to one or several consumers.
According to a further aspect of the invention, the filter material is filled into a pressure vessel. The compact filter material is located in a column at mid-height of the pressure vessel. The roof runoff water is fed under pressure from the water storage device above the filter material, flows through the filter material and reaches, at the bottom of the filter material, the discharge pipe that traverses the filter material, wherefrom it can be supplied to a consumer.
It is useful to equip the water storage device with a level control in order to protect the pump from running dry.
According to a further aspect of the invention, a foreign body trap is provided upstream from the water storage device, preferably in the downpipe of the gutter system. This trap separates large particles such as leaves, sticks, and dirt, and the roof runoff water thus pre-cleaned is then conducted into the water storage device. Dirty water in an amount of about 10% of the roof runoff water can be drained into the sewerage system without any problem, without causing any relevant environmental pollution.
The overflow ensures that no storage problems occur even in the event of large amounts of roof runoff water.
According to another aspect of the invention, a suction basket with a suction hose coupled to the pump is provided in the water storage device. This arrangement additionally ensures that no large dirt particles reach the filter material via the pump, causing it to clog.